Abrading – Flexible-member tool – per se – Interrupted or composite work face
Reexamination Certificate
2001-03-27
2002-12-03
Eley, Timothy V. (Department: 3723)
Abrading
Flexible-member tool, per se
Interrupted or composite work face
C451S228000, C451S527000, C451S528000
Reexamination Certificate
active
06488575
ABSTRACT:
TECHNICAL FIELD
The present invention relates to polishing pads for planarizing microelectronic-device substrate assemblies, and to methods for making and using such polishing pads in mechanical and/or chemical-mechanical planarization processes.
BACKGROUND OF THE INVENTION
Mechanical and chemical-mechanical planarizing processes (collectively “CMP”) are used in the manufacturing of electronic devices for forming a flat surface on semiconductor wafers, field emission displays and many other microelectronic-device substrate assemblies. CMP processes generally remove material from a substrate assembly to create a highly planar surface at a precise elevation in the layers of material on the substrate assembly.
FIG. 1
schematically illustrates an existing web-format planarizing machine
10
for planarizing a substrate assembly
12
. The planarizing machine
10
has a support table
14
with a top panel
16
at a workstation where an operative portion (A) of a polishing pad
40
is positioned. The top panel
16
is generally a rigid plate to provide a flat, solid surface to which a particular section of the polishing pad
40
may be secured during planarization.
The planarizing machine
10
also has a plurality of rollers to guide, position and hold the polishing pad
40
over the top panel
16
. The rollers include a supply roller
20
, first and second idler rollers
21
a
and
21
b
, first and second guide rollers
22
a
and
22
b
, and a take-up roller
23
. The supply roller
20
carries an unused or preoperative portion of the polishing pad
40
, and the take-up roller
23
carries a used or postoperative portion of the polishing pad
40
. Additionally, the first idler roller
21
a
and the first guide roller
22
a
stretch the polishing pad
40
over the top panel
16
to hold the polishing pad
40
stationary during operation. A motor (not shown) drives at least one of the supply roller
20
and the take-up roller
23
to sequentially advance the polishing pad
40
across the top panel
16
. As such, clean preoperative sections of the polishing pad
40
may be quickly substituted for used sections to provide a consistent surface for planarizing and/or cleaning the substrate assembly
12
.
The web-format planarizing machine
10
also has a carrier assembly
30
that controls and protects the substrate assembly
12
during planarization. The carrier assembly
30
generally has a substrate holder
32
to pick up, hold and release the substrate assembly
12
at appropriate stages of the planarizing cycle. A plurality of nozzles
33
attached to the substrate holder
32
dispense a planarizing solution
44
onto a planarizing surface
42
of the polishing pad
40
. The carrier assembly
30
also generally has a support gantry
34
carrying a drive assembly
35
that translates along the gantry
34
. The drive assembly
35
generally has an actuator
36
, a drive shaft
37
coupled to the actuator
36
, and an arm
38
projecting from the drive shaft
37
. The arm
38
carries the substrate holder
32
via another shaft
39
such that the drive assembly
35
orbits the substrate holder
32
about an axis B—B offset from a center point C—C the substrate assembly
12
.
The polishing pad
40
and the planarizing solution
44
define a planarizing medium that mechanically and/or chemically-mechanically removes material from the surface of the substrate assembly
12
. The web-format planarizing machine
10
typically uses a fixed-abrasive polishing pad in which abrasive particles are fixedly bonded to a suspension material. In fixed-abrasive applications, the planarizing solution is generally a “clean solution” without abrasive particles because the abrasive particles are fixedly distributed across the planarizing surface
42
of the polishing pad
40
. In other applications, the polishing pad
40
may be a nonabrasive pad composed of a polymeric material (e.g., polyurethane), a resin, or other suitable materials without abrasive particles. The planarizing solutions
44
used with nonabrasive polishing pads are typically CMP slurries with abrasive particles and chemicals to remove material from a substrate.
To planarize the substrate assembly
12
with the planarizing machine
10
, the carrier assembly
30
presses the substrate assembly
12
against the planarizing surface
42
of the polishing pad
40
in the presence of the planarizing solution
44
. The drive assembly
35
then orbits the substrate holder
32
about the offset axis B—B to translate the substrate assembly
12
across the planarizing surface
42
. As a result, the abrasive particles and/or the chemicals in the planarizing medium remove material from the surface of the substrate assembly
12
.
CMP processes should consistently and accurately produce a uniformly planar surface on the substrate assembly
12
to enable precise fabrication of circuits and photo-patterns. During the fabrication of transistors, contacts, interconnects and other components, many substrate assemblies develop large “step heights” that create a highly topographic surface across the substrate assembly
12
. To enable the fabrication of integrated circuits with high densities of components, it is necessary to produce a highly planar substrate surface at several stages of processing the substrate assembly
12
because nonplanar substrate surfaces significantly increase the difficulty of forming submicron features. For example, it is difficult to accurately focus photo-patterns to within tolerances approaching 0.1 &mgr;m on nonplanar substrate surfaces because submicron photolithographic equipment generally has a very limited depth of field. Thus, CMP processes are often used to transform a topographical substrate surface into a highly uniform, planar substrate surface.
In the competitive semiconductor industry, it is also highly desirable to have a high yield in CMP processes by quickly producing a uniformly planar surface at a desired endpoint on a substrate assembly
12
. For example, when a conductive layer on a substrate assembly
12
is under-planarized in the formation of contacts or interconnects, many of these components may not be electrically isolated from one another because undesirable portions of the conductive layer may remain on the substrate assembly
12
over a dielectric layer. Additionally, when a substrate assembly
12
is over planarized, components below the desired endpoint may be damaged or completely destroyed. Thus, to provide a high yield of operable microelectronic devices, CMP processing should quickly remove material until the desired endpoint is reached.
One technique to improve die performance of CMP processing is to use fixed-abrasive pads (FAPs) with a clean planarizing solution instead of nonabrasive pads with abrasive slurries. One problem with abrasive slurries is that the slurry may not uniformly contact the face of a substrate assembly
12
because the leading edge of the substrate assembly
12
wipes the slurry off of the pad
40
. As a result, more abrasive particles generally contact the edge of the substrate
12
assembly than the center, causing a center-to-edge planarizing profile. FAPs seek to resolve this problem by fixedly attaching the abrasive particles to the pad in a desired distribution. By fixing the abrasive particles to the pad instead of suspending the abrasive particles in the slurry, the center of the substrate assembly
12
contacts a large number of abrasive particles irrespective of the distribution of planarizing solution between the pad and the substrate assembly
12
. Using FAPs, however, presents some drawbacks in CMP processing.
One drawback of existing FAPs is that the abrasive particles in the FAPs may not adequately planarize substrate assemblies with very small components (e.g., components with a dimension of 0.25 &mgr;m or less). Existing FAPs are typically fabricated by covering a Mylar® or polyurethane backing film with a layer of resin and abrasive particles. The resin is then cured, and the layer of cured resin and abrasive particles may be textured. The particle size d
Agarwal Vishnu K.
Meikle Scott G.
Dorsey & Whitney LLP
Eley Timothy V.
Grant Alvin J.
Micro)n Technology, Inc.
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